Iraqi police say multiple bomb blasts have killed at least six people and wounded more than a dozen others in the Iraqi shrine city of Karbala, about 80 kilometers south of the capital, Baghdad.

Police say a bomb exploded outside the offices where passport and identity cards are issued. Officials say other blasts went off when emergency responders arrived.

The attacks come as the United States moves ahead with plans to withdraw its troops from Iraq by the end of the year. Violence is down from its height in 2006 and 2007, but both U.S. and Iraqi officials have expressed concern about Iraq's ability to cope with security after a U.S. withdrawal.